Definition | Causes | Risk Factors | Symptoms | Diagnosis | Treatment | Prevention

Definition

A blister is a fluid-filled bump on the skin.

Blisters

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Causes

Causes of blisters include:

  • Friction or constant pressure, such as from wearing a tight-fitting shoe or gripping a tool
  • Second-degree burns, including sunburn
  • Viral infections, such as chickenpox or shingles
  • Fungal infections such as athlete’s foot
  • Contact dermatitis, such as poison ivy or oak
  • Allergic reactions, drug reactions, certain cancers, and inflammatory conditions
  • Severe skin swelling, especially of the legs

Risk Factors

Factors that increase your chance of getting blisters include:

  • Wearing ill-fitting shoes
  • Repetitive work with hand tools
  • Getting a sunburn

Symptoms

Symptoms may include:

  • Fluid-filled bump on the skin, which is often round
  • Fluid is usually clear, but may be bloody

Diagnosis

You can diagnose a blister by its appearance and by the activity you were doing when it appeared. Seek medical attention if the blister is unusually painful, appears infected, or occurs with a burn.

Treatment

A blister will often heal without treatment. Some general tips for treatment include:

Protect the Area

  • Be gentle with the injured area. To prevent further injury, put a bandage over the affected area. The blister should begin to shrink in about seven days.
  • Do not pop or lance the blister. Opening the blister increases the chance of infection and delays healing.
  • In the case of poison ivy or a viral infection, do not scratch the blister. If necessary, call your doctor for medicine to relieve any itching or discomfort.

Wash the Area

If the blister is closed, wash the area with soap and water. Apply a bandage to protect it. If the blister is open, wash the area, apply an antibiotic ointment, and then cover it with a sterile dressing or bandage.

See Your Doctor If:

A blister usually heals by itself. See your doctor if:

  • The blister is unusually large (for example, bigger than a nickel)
  • The blister is in a critical area, such as on the face or the groin
  • The blister is associated with a burn
  • There are signs of infection, such as increasing redness around the blister, red streaks, severe swelling, pus drainage, fever, or an increase in pain

Prevention

To help prevent blisters:

  • Wear shoes that fit properly.
  • Always wear socks with your shoes.
  • Use gloves or protective padding when working with tools.
  • Wear a hat, protective clothing, and sunscreen when out in the sun.